Morphohistochemical characteristics of structures of the esophageal cross-striated muscle tissue]

On the bases of histochemical enzymatic studies and morphometric investigations, some differences were revealed between cross-striated esophageal muscular tissue and other skeletal muscles of mammals. A peculiar feature of the esophageal musculature is prevalence of unitypical fibres with small diameter and possessing high activity of oxidating enzymes. According to these signs, esophageal myons can be ascribed to the first type of muscular fibres. Simultaneously, a high activity of myofibrillar ATPh is revealed in them. Thus, according to histochemical indices, cross-striated esophageal muscular fibres of mammals are quick and slowly fatiqued fibres.     

Effects of denervation and direct electrical stimulation upon the post-hatching differentiation of posterior latissimus dorsi muscle in chicken

The influences of denervation and of direct electrical stimulation of denervated muscle upon the post-hatching differentiation of fibre types in the fast avian muscle posterior latissimus dorsi have been investigated. Denervation inhibits the normal decrease in number of muscle fibres exhibiting acid-stable myofibrillar ATPase activity and leads to weak oxidative activity in all the fibres. Direct stimulation at a low rhythm of denervated muscle induces the normal decrease of fibres exhibiting acid-stable myofibrillar ATPase but does not allow the occurrence of normal oxidative activity pattern. The results emphasize the role of muscular activity upon the differentiation of fibre types in a developing muscle.     

Observations on the fate of muscle fibres temporarily isolated by transection of a muscle belly

Summary Transection of the sternohyoid muscle of the rat has been used as an experimental situation in which the fate of the portions of fibre isolated from their nerve supply by the lesion can be studied. Sections from the muscle were stained to demonstrate oxidative and glycolytic enzymes and cholinesterase. Biopsies performed after periods of up to ten weeks after operation revealed a series of changes that suggested that after passing through the early stages of denervation atrophy recovery of the fibres took place. There was no indication that new motor end-plates were formed among the isolated fibres and it was concluded that communication had been reestablished with innervated fibres and that this reunion had been followed by a redetermination of the metabolic activity of the isolated fibres.I would like to thank Professor J. Z. Young for his advice and encouragement and Mrs. C. A. Joseph for her histochemical preparations.     

Maternal treatment with somatotropin during early gestation affects basic events of myogenesis in pigs

The effects of maternal treatment with somatotropin during early gestation on fetal muscle development were determined. Crossbred gilts received daily injections of either 3 ml of a placebo ( n=31) or of 6 mg porcine somatotropin ( n=31) from day (d) 10 to 27 of gestation and samples were collected from d 28 embryos, d 37 and 62 fetuses, and from neonates. Administration of somatotropin increased the total number of fibres (primary and secondary fibres) in neonatal semitendinosus muscle of middle- and low-weight littermates, whilst no increase was observed in psoas major muscle. Somatotropin induced increases in muscular protein concentration, creatine kinase activity, muscle fibre girth, as well as type II to type I fibre conversion which revealed an advanced degree of differentiation at birth. Treatment effects on prenatal development preceded these changes. Increased DNA concentrations at d 28 of gestation indicate stimulation of cellular proliferation during the embryonic stages. Thereafter, the withdrawal of somatotropin caused a transient delay of differentiation as indicated by lower protein concentrations and creatine kinase activity compared with controls at d 37 of gestation. This was compensated again at d 62, and the number of semitendinosus primary fibres was increased in middle-weight fetuses, whereas secondary or total fibre number did not yet differ. However, enhanced expression of Myf5 and MyoD indicates higher numbers of initially determined, proliferating myoblasts that may have contributed to increased formation of secondary fibres. In conclusion, maternal somatotropin is an influential factor in early pregnancy capable of affecting the basic events of myogenesis.     

Methods for demonstration of enzyme activity in muscle fibres at the muscle/bone interface in demineralized tissue

A method for demonstration of activity for ATPase and various oxidative enzymes (succinic dehydrogenase, alpha-glycerophosphate dehydrogenase, and lactic dehydrogenase) in muscle/bone sections of fixed and demineralized tissue has been developed. It was found that it is possible to preserve considerable amounts of the above mentioned enzymes in the muscle fibres at the muscle/bone interfaces. The best results were obtained after 20 min fixation, and 2-3 weeks of storage in MgNa2EDTA containing media. As the same technique previously has been used to describe patterns of resorption and deposition with the aid of a mapping of presence of phosphomonoesterases on bone surfaces, the method may be used to study possible biochemical interactions between bone and muscle tissue at the muscle/bone interface.     

Sexual differences in the increase of white muscle fibres in Argentine hake, Merluccius hubbsi, from the San Matias Gulf (Argentina)

Growth dynamics of white fibres from axial muscle has been investigated in Argentine hake, Merluccius hubbsi , discriminating between sexes for the first time. The frequency distributions of fibre diameters are remarkably different in both sexes at sizes between 42 and 63·9 cm total length (T.l.). Males have a much lower proportion of newly recruited fibres (0–10 μm) than females; at 52–53·9 cm T.l., females have 4% of fibres in that category and males 0·5%. It appears that, from this size interval onwards, the increase in muscle mass is due only to the increase in diameter of individual fibres, which may exceed 300 μm. The lower recruitment rate of new fibres in males, and its relationship to lower growth rates and smaller final sizes, are discussed, and possible effects of reproductive activity are considered.     

Activity patterns of phosphofructokinase,glyceraldehydephosphate dehydrogenase,lactate dehydrogenase and malate dehydrogenase in microdissected fast and slow fibres from rabbit psoas and soleus muscle

Summary Methods for standardized determination of phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in nanogram samples of microdissected single fibres of rabbit psoas and soleus muscle are described. Fast and slow fibres in soleus muscle show lower absolute activities of these enzymes than the respective fibre types in psoas muscle. Slow fibres represent a more uniform population in the two muscles according to absolute and relative activities of the enzymes investigated. Slow fibres are characterized by high activities of MDH and relatively low activities of glycolytic enzymes. Fast fibres in the soleus muscle represent a population with high activities of MDH and glycolytic enzymes. Fast fibres in psoas muscle represent a heterogeneous population with high activities of glycolytic enzymes and extremely variable activity of MDH. More than 10-fold differences exist in the MDH activities of the extreme types of this fibre population. Differences in the activity levels of MDH in single fast type fibres but also in the activities of glycolytic enzymes between fast and slow fibres are greater than those reported between extreme white and red rabbit muscles.     

Activity patterns of phosphofructokinase, glyceraldehydephosphate dehydrogenase, lactate dehydrogenase and malate dehydrogenase in microdissected fast and slow fibres from rabbit psoas and soleus muscle.

Methods for standardized determination of phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in nanogram samples of microdissected single fibres of rabbit psoas and soleus muscle are described. Fast and slow fibres in soleus muscle show lower absolute activities of these enzymes than the respective fibre types in psoas muscle. Slow fibres represent a more uniform population in the two muscles according to absolute and relative activities of the enzymes investigated. Slow fibres are characterized by high activities of MDH and relatively low activities of glycolytic enzymes. Fast fibres in the soleus muscle represent a population with high activities of MDH and glycolytic enzymes. Fast fibres in psoas muscle represent a heterogeneous population with high activities of glycolytic enzymes and extremely variable activity of MDH. More than 10-fold differences exist in the MDH activities of the extreme types of this fibre population. Differences in the activity levels of MDH in single fast type fibres but also in the activities of glycolytic enzymes between fast and slow fibres are greater than those reported between extreme white and red rabbit muscles.     

Growth dynamics of caudal and pectoral fin muscle fibres in a carangid, Caranx malabaricus (Cuv. & Val.), and their possible relation with somatic growth

The growth dynamics of red, pink and white fibres of the caudal and pectoral fin muscles are described in Carans malabaricus (Cuv. & Val.) in relation to their somatic growth. In all three fibre types growth occurred by an increase in fibre number and diameter in small size classes of fish and by an increase in diameter only in larger fish. The growth dynamics of the three fibre types were similar to those of the myotomal muscle fibres and paralleled the somatic growth pattern of this fish.     

Quantitative succinate-dehydrogenase histochemistry. III. Variations in histochemical succinatedehydrogenase activity in different cross-sections of the same muscle fibre.

The variation in histochemical SDH-activity at different levels in the same muscle fibre was determined in muscle fibre cross-sections both by visual classification and quantitative determination of the formazan-deposits. This work resulted in a confirmation of the earlier micro-biochemical studies of Spamer AND Pette (1977, 1979) and Lowrey et al. (1978) that the activity of enzymes of the citric acid cycle is not homogeneously distributed in a muscle fibre over its entire length. In addition it is shown that the observed variations in histochemical SDH-activity strongly interfere with the visual muscle fibre typing. Some of the possible causes for these variations in histochemical SDH-activity (section-thickness, presence of the motor-endplate) and the implications of these findings for the relation between histochemical characteristics and functional properties of the muscle fibres are briefly discussed.     

Development of chequerboard pattern in human foetal skeletal muscle.

The study was undertaken to race the histochemical and electron microscopic development patterns of human myogenesis from the 9th to the 26th week of foetal life. Particular attention was paid to the possibility of appearance of metabolic or structural differences between individual skeletal muscle fibres in early periods of myogenesis. The 9th week of foetal life is the period when primitive myotubes are formed. Irregular distribution of the ATPase (pH 9-4) activity observed at this time is due to differences in the structure of fusing myoblasts. The early myotubes show a high activity of the oxidative enzymes and lack of phosphorylase. Conversion of immature muscle cells into structurally mature fibres begins between the 20th and the 24th week. The latter fibres exhibit a uniform activity of all the studied enzymes and thus resemble the intermediate type of fibres of mature muscles. From about the 26th week on the typical mosaic pattern of the enzymatic activity is observed. All the differences in enzymatic activity which appear in fibers prior to their full morphologicaal maturity result from differences in developmental stages of the fibres at the given moment. The present study also suggests that there are no morphological or metabolic differences between individual humanskeletal muscle fibres prior to their metabolic differentiation into types which occurs after their innervation.     

The value of enzyme histochemical techniques in the classification of fibre types of human skeletal muscle

Summary Classification of human skeletal muscle into type I and type II fibres is frequently based on their weak or strong staining with the myosin adenosine triphosphatase reaction. In order to evaluate the reliability of this screening technique a combined histochemical and biochemical study was performed on normal and diseased skeletal muscle of human subjects. In the present investigation activities of enzymes which play a role in the aerobic and anaerobic pathways and which can characterize fibre type, were examined in human muscle specimens with disease of the neuromuscular system.Special attention is given to the maximal activities of phosphofructokinase and fructose-1,6-diphosphatase, the rate limiting enzymes for the regulation of the glycolysis and gluconeogenesis respectively. Moreover the activities of enzymes of the pentose phosphate pathway are determined.A most important feature of the biochemical findings is that the constancy of activity ratios of the examined enzymes, as is found apparently normal human skeletal muscle, was frequently not present in diseased human skeletal muscle. From these results and from the histochemical results it can be concluded that for fibre classification in diseased human skeletal muscle the histochemical demonstration of myosin ATPase activity exclusively is not sufficient, but that it is necessary to apply other enzyme histochemical techniques too.Moreover it was found that in diseased human skeletal muscles the activity of the NADPH regenerating enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase was strongly increased. A third observation was the relative decrease of the activity of the examined aerobic enzymes in affected muscle fibres of neurogenic muscle diseases.     

Mathematical analysis of myelin structure of nerves of the brachial plexus in antenatal and early postnatal ontogenesis of man]

A gradual increase of the information entropy indices and a decrease of the excess percentage is observed in the course of antenatal and early postnatal ontogenesis of man. The indices of the information entropy reach their maximum and the excess percentage reaches its minimum in children younger than 3 years. At that time the myelinated fibres have the most various diameters. In the antenatal development of man the prevalence of fine (1--4 mkm) myelinated fibres makes the structure of the humeral plexus nerves more definite while in the postnatal ontogenesis their structure is less definite since the myelinated fibres of different diameter are met with almost the same probability.     

The effect of reinnervation on the distribution of muscle fibre types in the tibialis anterior muscle of the mouse

The distribution of fibre types in the tibialis anterior (TA) muscle of adult mice was examined by means of an immunohistochemical approach, using monoclonal antibodies that recognize different myosin heavy chain isoforms. As has been reported previously, the superficial portion of TA contains almost exclusively type IIB fibres and is almost entirely glycolytic in nature. Following section of the lateral popliteal nerve and rotation of the proximal stump to prevent rematching, it was found that the original pattern was virtually restored within 2 months. One possible explanation for this observation is that the activity pattern of peripheral and deep muscle fibres differs and that this aids in specification of muscle fibre type. Alternatively, the muscle fibres of the superficial portion of TA may be inherently resistant to an alteration of their phenotype with regard to expression of myosin heavy chain.     

Extracellular recording of localized electrical activity in denervated frog slow muscle fibres

Pyriformis muscles of Rana temporaria were denervated by cutting the sciatic nerve in the pelvis. Slow muscle fibres were depolarized with intracellular current pulses, and the electrical activity was recorded simultaneously with intracellular and extracellular recording electrodes. When the extracellular electrode was moved along the fibre surface, outward and inward currents of variable amplitude were recorded. Inward currents coincided with the fast rising phase of the intracellularly recorded action potential; up to four inward current peaks could be detected in single fibres investigated over 3.4--8 mm of their length. The distance between inward current peaks was generally 1--2 mm, but greater distances were also observed. Composite action potentials could be shown to be due to inward currents arising in separate areas of the slow fibre membrane. It is concluded that after denervation Na-channels are incorporated into spatially limited areas of the membrane of slow muscle fibres.     

Growth dynamics of white myotomal muscle fibres in the bluntnose minnow, Pimephales notatus Rafinesque, and comparison with rainbow trout, Salmo gairdneri Richardson

The dynamics of increase of the predominant white muscle fibres of the myotomal bulk in bluntnose minnow, Pimephales notatus , ranging from 2.0 to 9.1 cm f.l. have been analysed by examination of modal progression of fibre diameter frequency classes in fish fed to satiation and growing at different rates at 15, 25 or 30°C. Recruitment of new fibres appeared to contribute little to increase in muscle bulk above 4 cm f.l. , and nothing beyond 6 cm. The dominant means of increase was increase in fibre diameter. The limiting fibre diameter seemed to be 120 μ. These dynamics, which result in an approximately 1: 1 ratio between mean fibre diameter and f.l. , are in contrast to those of the myotomal white muscle of rainbow trout, Salmo gairdneri , in which, regardless of differences in somatic growth produced by temperature, ration size or growth hormone administration, mean fibre diameter does not exceed that in bluntnose minnow until trout exceed 30 cm f.l. In trout there is, moreover, input of new fibres up to approximately 50 cm f.l. , when subsequent growth, as in the minnow, is by means of fibre diameter increase. The bluntnose minnow is a small, slow growing species; the rainbow trout is a large, fast growing species. The discussion links these facts with the observed differences in fibre growth dynamics in relation to a hypothesis of interspecific differences in fish growth capability.     

Effects of electrical stimulation upon post-hatching development of fibre types in normally innervated fast and slow latissimus dorsii muscles of the chicken

In chicken, the main characteristic properties of muscle fibre types in slow anterior (ALD) and fast posterior (PLD) latissimus dorsii are acquired during post-hatching development. At day 4 it becomes possible to distinguish between alpha' and beta' fibre types in ALD muscle. At the same time, mATPase staining and NADH-TR activity permit recognition of alpha w and alpha R fibres within PLD muscle. During further development, muscle fibre typology progressively changes towards the adult slow and fast type. Chronic stimulation at a slow rhythm (5 Hz) of PLD prevents the change in relative proportions of alpha R and alpha W fibres within the muscle that occurs in normal post-hatching development and increases the number of beta R fibres. Moreover, oxidative activity is increased in all muscle fibre types following stimulation. In ALD muscle, chronic stimulation at a fast rhythm (40 Hz) results in a decrease in oxidative activity and inhibits the differentiation of alpha' and beta' muscle fibre types. This study demonstrates that in young chicken, the pattern of activity influences the differenciation of fibre types in slow and fast muscles.     

Morphology of muscle fibres in amphibian submandibular muscle

The microscopic organization and ultrastructure of the submandibular muscle of 10 species of Amphibia were compared. Among other fibre features the diameter of fibres, their content of mitochondria and fat, organization of sarcomeres: morphology of Z-line, M-band and sarcoplasmic reticulum were taken into consideration and 4 main types of muscle fibres were distinguished. They correspond to tonic (slow) and phasic (red, white and intermediate) ones. Slight variety of fibre morphology and of fibre elements among the examined species was found. Special attention to the variety of fibre morphology among the established types has been paid and the existence of continuous "spectrum" of fibres was suggested. The correlation of frequency of fibres of particular types with the body size, gular oscillation frequency, and some other characteristics of the submandibular muscle in the examined species was discussed. Also the zonal arrangement of muscle according to the fibre types, as well as possible dynamic nature of muscle fibres were emphasised.     

The larval development of lateral musculature in gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax

Fibre-type differentiation of the lateral musculature has been studied in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval development. Histochemical and ultrastructural techniques show two presumptive muscle layers and two germinative zones of presumptive myoblasts. At hatching, myotomal muscle consists of a monolayer of thin undifferentiated cells near the skin (first germinative zone) overlying another mono-layer of small diameter fibres extending hypaxially and epaxially away from the transverse septum. Below this, there is a much thicker, deep layer of fibres, generally large in diameter and polygonal in shape. The presumptive myoblasts are located between these two layers of fibres in the second germinative zone. Initially, the superficial and deep muscle fibres show high and low myosin ATPase activity, respectively. Both layers grow by generating new fibres from the two mentioned germinative zones. At the end of larval life, the superficial layer changes its histochemical profile from high to low myosin ATPase activity and, at the same time, intermediate or pink muscle fibres can be observed by oxidative activity (the NADH-TR reaction). Morphometric analysis shows a significant increase in mean fibre diameter during successive ages, as shown by the Student's t-test (hypertrophic growth). Skewness and kurtosis values of fibre diameters point to the generation of a new fibre population from the germinative zones (hyperplastic growth).     

An approach to measuring change in muscular tissue contraction

In this paper the authors consider a histological muscular component from the point of view of systems theory. Of the smooth and striated types of muscular fibres, the latter have a structural component that permits them to contract. Unlike the visceral striated and cardiac fibres, movements in the skeletal striated fibres are predominantly voluntary. An overlapping of certain fibre components--specifically a sliding movement of the filaments of which the fibre is composed--causes a variation in the overall size of the fibre and therefore of the muscle. The distances covered, whether in contraction or lengthening, vary according to the type of fibre from 1.8 to 3.8 microm, but depend only on the capacity of some filaments to slide over other filaments, with filament size itself remaining unchanged. Our objective is to obtain a metric of this system that will permit us to obtain some idea of the degree of variation in these distances. In future projects it will be possible to extend this theory to other involuntary muscular tissue movements (myocardial tissue, e.g.), in an endeavour to develop a mathematical approach to the study of myocardial processes damaged by electrical conduction problems.